Bad is_sorted docs

[BenFrantzDale]

In https://github.com/boostorg/range/blob/develop/doc/reference/algorithm_ext/is_sorted.qbk:

For the non-predicate version the return value is `true` if and only if for
each adjacent elements `[x,y]` the expression `x < y` is `true`.
For the predicate version the return value is `true` is and only if for each
adjacent elements `[x,y]` the expression `pred(x,y)` is `true`.

note that's describing a strict ordering, which would treat 0, 0 as not sorted!

I think it should read

For the non-predicate version the return value is `true` if and only if for
each adjacent elements `[x, y]` the expression `y < x` is `false` (i.e., `x <= y`), or if the number of elements is zero or one.
For the predicate version the return value is `true` is and only if for each
adjacent elements `[x, y]` the expression `pred(y, x)` is `false`, or if the number of elements is zero or one.